Table 1.
Rate Ratios of Encephalopathy, Unspecified Dementia, and Combined Encephalopathy and Unspecified Dementia Following Styrene Exposure Among 72,465 Workers in the Danish Reinforced Plastics Industry, 1977–2011
| Styrene Exposure Metric | Encephalophathy | Unspecified Dementia | Combined Encephalopathy and Unspecified Dementia | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Person-Years | Cases | RR a | 95% CI | RR b | 95% CI | Cases | RR a | 95% CI | RR b | 95% CI | Cases | RR a | 95% CI | RR b | 95% CI | |
| Cumulative exposure, mg/m3-years | ||||||||||||||||
| <18 | 498,700 | 40 | 1.00 | 1.00 | 124 | 1.00 | 1.00 | 164 | 1.00 | 1.00 | ||||||
| 18–71 | 498,987 | 70 | 1.56 | 1.06, 2.31 | 1.26 | 0.85, 1.86 | 187 | 0.97 | 0.77, 1.22 | 1.03 | 0.81, 1.29 | 257 | 1.11 | 0.91, 1.36 | 1.09 | 0.90, 1.34 |
| >71 | 498,907 | 118 | 2.55 | 1.77, 3.66 | 1.90 | 1.31, 2.77 | 254 | 0.86 | 0.69, 1.07 | 0.98 | 0.78, 1.23 | 372 | 1.17 | 0.97, 1.41 | 1.17 | 0.96, 1.42 |
| P for linear trend | <0.01 | <0.01 | 0.13 | 0.78 | 0.12 | 0.11 | ||||||||||
| Mean exposure probability | ||||||||||||||||
| <0.23 | 497,945 | 66 | 1.00 | 1.00 | 224 | 1.00 | 1.00 | 290 | 1.00 | 1.00 | ||||||
| 0.23–0.58 | 497,489 | 70 | 1.14 | 0.81, 1.60 | 0.88 | 0.63, 1.25 | 205 | 1.05 | 0.87, 1.27 | 0.98 | 0.80, 1.19 | 275 | 1.07 | 0.91, 1.26 | 0.94 | 0.79, 1.12 |
| >0.58 | 501,160 | 92 | 1.67 | 1.21, 2.30 | 1.41 | 1.01, 1.96 | 136 | 0.99 | 0.80, 1.22 | 0.89 | 0.71, 1.11 | 228 | 1.19 | 1.00, 1.41 | 1.03 | 0.86, 1.23 |
| P for linear trend | <0.01 | 0.03 | 0.98 | 0.32 | 0.06 | 0.81 | ||||||||||
| Mean exposure intensity, mg/m3 | ||||||||||||||||
| <12 | 498,858 | 50 | 1.00 | 1.00 | 108 | 1.00 | 1.00 | 158 | 1.00 | 1.00 | ||||||
| 12–40 | 497,914 | 73 | 1.25 | 0.87, 1.80 | 0.88 | 0.60, 1.27 | 217 | 1.08 | 0.85, 1.36 | 1.11 | 0.87, 1.41 | 290 | 1.13 | 0.93, 1.38 | 1.05 | 0.86, 1.29 |
| >40 | 499,822 | 105 | 1.83 | 1.31, 2.58 | 1.18 | 0.82, 1.68 | 240 | 0.98 | 0.77, 1.23 | 1.05 | 0.82, 1.34 | 345 | 1.17 | 0.96, 1.42 | 1.08 | 0.88, 1.33 |
| P for linear trend | <0.01 | 0.21 | 0.64 | 0.90 | 0.13 | 0.47 | ||||||||||
| Duration of employment, years | ||||||||||||||||
| 1 | 686,337 | 90 | 1.00 | 1.00 | 248 | 1.00 | 1.00 | 338 | 1.00 | 1.00 | ||||||
| 2–4 | 552,064 | 66 | 0.89 | 0.65, 1.22 | 0.98 | 0.71, 1.35 | 193 | 0.89 | 0.74, 1.08 | 0.96 | 0.79, 1.16 | 259 | 0.89 | 0.76, 1.05 | 0.95 | 0.81, 1.12 |
| ≥5 | 258,193 | 72 | 1.80 | 1.32, 2.46 | 2.19 | 1.58, 3.02 | 124 | 0.73 | 0.59, 0.91 | 0.83 | 0.66, 1.03 | 196 | 0.94 | 0.79, 1.13 | 1.06 | 0.88, 1.27 |
| P for linear trend | <0.01 | <0.01 | <0.01 | 0.10 | 0.40 | 0.68 | ||||||||||
Abbreviations: CI, confidence interval; RR, rate ratio.
a Adjusted for age.
b Adjusted for age, calendar year, sex, level of education, hospitalizations related to chronic obstructive pulmonary disease, alcohol-related hospitalizations, and employment status.